I. Field of the Invention
The present invention relates to the field of computer firmware, interface cards, PCMCIA cards and the like.
II. Description of Related Art:
In a computer system, interface cards are provided between data communication devices and data processing terminal devices to ensure proper communication between the devices. An interface card may reside between a system bus and user interface devices such as a keyboard, a mouse or other pointing devices and a display of the computer system. In another instance, an interface card may reside between the system bus and a modem, another computer, a network, or an instrument for measuring various parameters in a laboratory or a manufacturing facility.
Various interface standards are used in the industry to standardize methods of communication and to ensure uniformity. One is the PCMCIA PC card standard whose release #2.01 is enclosed herewith. The PCMCIA specification defines the number of pins, the location of the pins and their functions. The present invention incorporates some of the standard PCMCIA signals.
Card information structure (CIS) bytes in an interface card contain information about the card. A computer host reads the CIS bytes to find out various information including, but not limited to, whether it is an I/O card, a memory card or a modem card, and who the manufacturer is. Prior art computer systems have provided either an internal CIS read or an external CIS read, but have not provided the capability to choose one or the other in a given system. In an internal CIS read, the CIS bytes typically reside in a chip where a microcontroller for the interface card resides. In an external CIS read, the CIS bytes are in another chip such as a memory chip.
In addition, prior art computer systems have fixed location and size of CIS bytes. For example, CIS bytes may be fixed to 0-100 h address locations. Also, PCMCIA registers such as configuration option register, card configuration and status register and pin replacement register organization have fixed address locations. If the CIS bytes need to be upgraded, and the new CIS bytes occupy more bytes than the original CIS bytes, the chip containing the CIS bytes needs to be replaced.
To overcome the drawbacks of the prior art interface cards, the present invention provides a firmware selectable location and size for CIS bytes and the ability to choose an internal or external CIS read. The present invention also allows a system designer to choose between a common memory mode for using the interface card as a memory card and an audio mode for using the interface card as an I/O card, utilizing only two external pins.